1. Field of the Invention
The present invention relates to an improved development station for an apparatus for the diazotype reproduction of originals, and to a diazotype reproduction apparatus incorporating such improved development station.
For the sake of convenience, the support sheet of paper or polymer film coated with a sensitive diazo layer will herein be referred to as the "copy", while the sheet of transparent or semi-transparent paper or polymer film bearing the graphic intelligence to be reproduced will be designated the "original".
2. Description of the Prior Art
Apparatus for the diazotype reproduction of originals typically comprises at least one exposure station, in which the copy is exposed to light through the original in order to form a latent image on the copy, and a development station, in which the copy bearing the latent image is contacted with a material for the development of the latent image, such that the latent image will become visible.
The material for the development of the latent image may be liquid or gaseous. In the present text, reference will more specifically be made to a development station wherein the material used to develop the latent image is a gas comprised of ammoniacal vapors.
The development station is provided with means for advancing the copy into a zone of the development station where the copy will be exposed to the action of the ammoniacal vapors.
The drive means and the means for contacting the copy with the ammoniacal vapors typically comprise driven endless belts, which define a plane or cylindrical surface in registration with the perforated surface of an elongate vessel, the length of which is at least equal to the useful width of the development station, the vessel being charged with the ammoniacal vapors.
On feeding between the belts and the perforated surface of the vessel, the copy bearing the latent image is thus driven by the belts and the latent image is developed by the ammoniacal vapors which pass through the perforations in the vessel.
The developed copy can then similarly advance between the belts and another vessel which has a perforated wall and which is maintained under negative pressure in order to eliminate the excess ammoniacal vapors present on the copy.
This type of construction of a development station generally gives satisfactory results, but it nonetheless has disadvantages.
Numerous problems in respect of gas-tightness indeed arise, insofar as said development vessels are concerned, and these development stations are often foul smelling. In addition, as the volume of the vessel through which the ammoniacal vapors pass is relatively great, and as the speed of the vapors contacting the sensitive coating must be high, substantial volumes of ammoniacal vapors are used, thereby increasing the size of the development station on the one hand and, on the other, also increasing the size of the ammoniacal vapor supply means, while a large volume of unused vapors has to be treated with an acid solution, which also increases the size of the neutralization equipment.